In "Fifty Shades of Grey," the first of E.L. James' romance novels to dominate the best-seller lists, the brooding Seattle billionaire Christian Grey informs his new paramour, Anastasia Steele, of his general lack of interest in "vanilla sex" – traditional, kink-free intercourse unmediated by cuffs, chains or any of the other instruments he keeps in his leather-padded Red Room of Pain.

In "Fifty Shades Freed," the third and final movie to be adapted from the series, Anastasia – played once more with heroic commitment by Dakota Johnson – unwittingly hits at a new definition of "vanilla sex." She and Christian (Jamie Dornan) are now married, and after raiding the freezer late one night, she shoves her husband against a table and initiates a little foreplay a la mode. I'm assuming it's vanilla ice cream she uses, judging by the color of the residue melting suggestively on his lower torso. The audience in my theater might have melted, too, if we weren't all so busy giggling.

It's hard not to giggle at the "Fifty Shades" movies, and I say that with as much admiration as exasperation. These are pictures that generously invite your laughter with their Architectural Digest trappings, their soapy excesses and their all-too-keen awareness of their own vapidity. There's also the fact that it's funny, if also a bit nervous-making, to see two gorgeous people enacting an underlighted, over-edited, meticulously choreographed, none-too-convincing pantomime of carnal ecstasy.

Even the rougher action on display here is vanilla sex, sweetly scented and artificially flavored. In contrast to James' unapologetically pornographic fiction, the lovemaking in these movies has been tamed into soft-core submission, hemmed in by R ratings and non-negotiable nudity clauses. Note how carefully the camera confines itself to tasteful shots of Dornan's rear or Johnson's breasts, always staying respectfully in the vicinity of North Dakota.

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Dreadful though these movies may be, they can also elicit a broader, more complicated range of feelings than a lot of ostensibly better, more respectable movies manage. Which is another reason why giggling, a conveniently noncommittal, all-encompassing response, comes in handy. A giggle can express delight as well as disdain, agony as well as ecstasy, which makes it an especially fitting way to engage with Christian, Anastasia and their tortured dialectic of pain versus pleasure.

That dialectic has admittedly become steadily less intriguing and more confusing with each movie. "Fifty Shades of Grey" (2015) had the good fortune to be directed by Sam Taylor-Johnson, working from a Kelly Marcel script that represented an immediate improvement on James' atrociously written text. The film brought out the sly, knowing comedy in Christian's aggressive seduction tactics and Anastasia's wary skepticism, all the while rubbing our faces in every shiny emblem of the Grey fortune: that penthouse! That helicopter! That clothing-optional grand piano!

The result was a better picture than it had any right to be, though its two sequels seem to have gone out of their way to make up the difference. Last year's misleadingly titled "Fifty Shades Darker," directed by James Foley and scripted by Niall Leonard (the author's husband), piled on the swoon-worthy luxury goods plus a few dubious thriller flourishes, even as it dragged out Anastasia's increasingly tedious ambivalence toward her adoring stalker of a boyfriend.

Now Foley and Leonard have given us the sublimely ridiculous "Fifty Shades Freed," which plunges a once purely transactional arrangement into full-on matrimonial bliss, starting with a wedding montage that all but asphyxiates the viewer with white lace.

How long after the honeymoon will Mr. and Mrs. Grey be able to sustain their life of hanky-spanky? Not long, if Anastasia's violently unhinged ex-boss, Jack Hyde (Eric Johnson, who seems to have dyed his eyeballs red), has anything to say about it. Really, though, Hyde's cartoon-villain resurgence may pose less of a threat to the Greys' happiness than Christian himself, who becomes even more impossibly possessive than usual.

There's some fun to be had along the way, especially when the newlyweds, taking the new Audi for a spin, find themselves being pursued by a sinister-looking SUV. With Anastasia behind the wheel and Christian barking directions from the passenger seat, the ensuing chase features as much dominant-submissive bump-and-grind as any of their Red Room romps. ("Get off here," he orders; she does.)

When Anastasia complains that her 24-7 security detail keeps her from seeing her best pal, Kate (Eloise Mumford), Christian impulsively whisks her and a few friends off to his Aspen, Colo., lodge, where Champagne flutes, bubble baths and aphrodisiac desserts await.

But most of the time Christian glowers and rages when he doesn't get his way, clearly having learned to flog his problems into submission rather than solve them. You may nod vigorously when he acknowledges he's not ready to have children, perhaps stemming from his conflicted feelings toward the birth mother he never knew. But the utterly daft scene in which he shows up unannounced at his wife's office, berating her for still using her maiden name in her corporate email address, exists on an entirely different level of heavy petulance. By the time Christian persuades Anastasia to insert a plug into her nether regions, you want to ask if he's ever bothered removing his.

It's about time he did, as the movie's title more or less suggests. But if liberation is the endgame of "Fifty Shades Freed," most of the time we feel trapped right alongside the characters, immobilized by the pointless, suffocating beauty and the stultifying dramatic inertia of the world James has created for them. Whenever a fresh or familiar face pops into view – like Christian's sweet, vivacious sister, Mia (pop singer Rita Ora), or their wise, imperious mother (Marcia Gay Harden) – you long for the movie to follow that person somewhere, to grant us a change of scenery that doesn't involve Christian and Anastasia's stunning new dream house, or a conversation that doesn't devolve into deathly dull innuendo.

The filmmakers have long stopped pretending to find anything troubling or transgressive about Christian's appetites – he might wield that vibrator a bit punitively at times, but really, who doesn't – leaving them little to do besides cut away distractedly to Hyde's harebrained scheme and usher the Greys toward the more ominous prospect of long-term commitment and parenthood. That's the real villain in this love story, of course: the threatening possibility that these two beautiful, enviable one-percenters might be headed for a more boring, more conformist existence than they think they deserve.

Boo-hoo, yawn-yawn, giggle-giggle. As we bid good riddance and "laters, baby" to the "Fifty Shades" franchise, it's hard to begrudge Christian and Anastasia their inevitable fairy-tale ending, or to wish these two game, likable actors anything but greener pastures. With any luck, the endearingly wooden Dornan will have better performances ahead of him, while Johnson, whose radiant intelligence and tremulous sensitivity have brought more shades to this story than anyone could have dreamed, will surely have better movies. The next time she suffers this vividly for her art, let's hope it's as good for her as it was for us.